redhat man page for spttrf

SPTTRF(l)								 )								 SPTTRF(l)

NAME
       SPTTRF - compute the L*D*L' factorization of a real symmetric positive definite tridiagonal matrix A

SYNOPSIS
       SUBROUTINE SPTTRF( N, D, E, INFO )

	   INTEGER	  INFO, N

	   REAL 	  D( * ), E( * )

PURPOSE
       SPTTRF computes the L*D*L' factorization of a real symmetric positive definite tridiagonal matrix A. The factorization may also be regarded
       as having the form A = U'*D*U.

ARGUMENTS
       N       (input) INTEGER
	       The order of the matrix A.  N >= 0.

       D       (input/output) REAL array, dimension (N)
	       On entry, the n diagonal elements of the tridiagonal matrix A.  On exit, the n diagonal elements of the diagonal matrix D from  the
	       L*D*L' factorization of A.

       E       (input/output) REAL array, dimension (N-1)
	       On entry, the (n-1) subdiagonal elements of the tridiagonal matrix A.  On exit, the (n-1) subdiagonal elements of the unit bidiago-
	       nal factor L from the L*D*L' factorization of A.  E can also be regarded as the superdiagonal of the unit bidiagonal factor U  from
	       the U'*D*U factorization of A.

       INFO    (output) INTEGER
	       = 0: successful exit
	       < 0: if INFO = -k, the k-th argument had an illegal value
	       >  0: if INFO = k, the leading minor of order k is not positive definite; if k < N, the factorization could not be completed, while
	       if k = N, the factorization was completed, but D(N) = 0.

LAPACK version 3.0						   15 June 2000 							 SPTTRF(l)